[PATCH AUTOSEL 6.14 551/642] bridge: mdb: Allow replace of a host-joined group

Sasha Levin
2025-05-05T22:36:30Z

From: Petr Machata <petrm@nvidia.com>

[ Upstream commit d9e9f6d7b7d0c520bb87f19d2cbc57aeeb2091d5 ]

Attempts to replace an MDB group membership of the host itself are
currently bounced:

# ip link add name br up type bridge vlan_filtering 1
# bridge mdb replace dev br port br grp 239.0.0.1 vid 2
# bridge mdb replace dev br port br grp 239.0.0.1 vid 2
Error: bridge: Group is already joined by host.

A similar operation done on a member port would succeed. Ignore the check
for replacement of host group memberships as well.

The bit of code that this enables is br_multicast_host_join(), which, for
already-joined groups only refreshes the MC group expiration timer, which
is desirable; and a userspace notification, also desirable.

Change a selftest that exercises this code path from expecting a rejection
to expecting a pass. The rest of MDB selftests pass without modification.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/e5c5188b9787ae806609e7ca3aa2a0a501b9b5c4.1738685648.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/bridge/br_mdb.c | 2 +-
tools/testing/selftests/net/forwarding/bridge_mdb.sh | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index 1a52a0bca086d..7e1ad229e1330 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -1040,7 +1040,7 @@ static int br_mdb_add_group(const struct br_mdb_config *cfg,

/* host join */
if (!port) {
- if (mp->host_joined) {
+ if (mp->host_joined && !(cfg->nlflags & NLM_F_REPLACE)) {
NL_SET_ERR_MSG_MOD(extack, "Group is already joined by host");
return -EEXIST;
}
diff --git a/tools/testing/selftests/net/forwarding/bridge_mdb.sh b/tools/testing/selftests/net/forwarding/bridge_mdb.sh
index d9d587454d207..8c1597ebc2d38 100755
--- a/tools/testing/selftests/net/forwarding/bridge_mdb.sh
+++ b/tools/testing/selftests/net/forwarding/bridge_mdb.sh
@@ -149,7 +149,7 @@ cfg_test_host_common()
check_err $? "Failed to add $name host entry"

bridge mdb replace dev br0 port br0 grp $grp $state vid 10 &> /dev/null
- check_fail $? "Managed to replace $name host entry"
+ check_err $? "Failed to replace $name host entry"

bridge mdb del dev br0 port br0 grp $grp $state vid 10
bridge mdb get dev br0 grp $grp vid 10 &> /dev/null
--
2.39.5